Mr Goff said he had not released electronic copies of the stadium report to councillors for fear it will be leaked to the media.

He said the report was commerically sensitive and that he was protecting third parties when he provided councillors with only printed copies.

There had been strong rumblings from councillors since the stadium report which only came to light after a RNZ appeal to the Ombudsman.

"This means, amongst other things, that over the period of nearly a year you have made no attempt to inform councillors as to the contents of the report or indeed that it had even been written.

"In our view this behaviour falls far short of the sort of transparency and inclusiveness we would expect in such a significant matter as this concerning a potential $1.5 billion stadium," the letter said.

The offer that was then made to councillors that they could have supervised access to the full report was "unsatisfactory, if not insulting", they wrote.

"If this was an isolated incident we might have been tempted to raise the appropriate objections and mark it down to experience.

"Unfortunately, however, this is reflective of a leadership style that has become increasingly apparent as the term has progressed," it said.